Fastener-driving tools, which may be pneumatically powered or combustion-powered, are used widely in building construction. Such pneumatically powered tools are exemplified in Golsch U.S. Pat. No. 4,932,480. Such combustion-powered tools are exemplified in Nikolich U.S. Patent Re. 32,452 and in Nikolich U.S. patent application Ser. No. 07/848,277 filed Mar. 9, 1992.
Typically, such a pneumatically powered or combustion-powered tool comprises a housing structure, a nosepiece extending from the housing structure, a primary actuating structure, and a secondary actuating structure. The primary actuating structure is movable between a tool-disabling position relative to the housing structure and a tool-enabling position relative thereto and is biased to the tool-disabling position. The secondary actuating structure is movably mounted upon the nosepiece. The primary actuating structure is arranged to enable the tool when such structure is moved to the tool-enabling position and to disable the tool when such structure is moved from the tool-enabling position. The secondary actuating structure is arranged to move the primary actuating structure to the tool-enabling position when the secondary actuating structure is pressed firmly against a workpiece. Typically, the fastener-driving tool also comprises a trigger, which must be manually actuated after the tool has been enabled by the primary actuating structure.
Commonly, such a fastener-driving tool is used for fastening new siding material, such as vinyl siding or aluminum siding, over an older building structure, which may have an irregular or undulating surface. Aesthetically, it is important for the lower surface of the siding material to be substantially flat and not to follow the contour of an irregular or undulating surface, over which the siding material may be applied. However, if a fastener is driven through the siding material, into an underlying structure where the underlying structure has a depression, to a maximum depth of penetration of the fastener, the fastener tends to draw the siding material into the depression.
Because the primary actuating structure is biased to the tool-disabling position, because the secondary actuating structure is movable conjointly with the primary actuating structure, and because the secondary actuating structure must be firmly pressed against the siding material to enable the tool, the tool cannot be moved away from the siding material by more than a very small distance without disabling the tool. It is not practicable, therefore, to change the depth of the penetration of the fastener to be driven next by moving the tool away from the siding material.
Hence, there has been a need for a fastener-driving tool enabling a user to drive successive fasteners to varying depths of penetration, as where new siding material is being applied over an irregular or undulating surface. This invention is addressed to that need.